Radiation-emitting semiconductor chip with overlapping contact layers

ABSTRACT

A radiation-emitting semiconductor chip includes a semiconductor body; a first contact layer having a first contact surface for external electrical contacting of the semiconductor chip and a first contact web structure connected to the first contact surface, wherein the first contact web structure is a region of the first contact layer that, compared to the first contact surface, has a comparatively small extent at least in a lateral direction; a second contact layer, wherein first and second contact web structures overlap in places in plan view of the semiconductor chip; a current distribution layer; and an insulation layer having a plurality of openings into which the current distribution layer extends.

TECHNICAL FIELD

This disclosure relates to a radiation-emitting semiconductor chip.

BACKGROUND

Different geometries are useful for different applications ofradiation-emitting semiconductor components such as light-emitting diodesemiconductor chips. Semiconductor chips with a large length-to-widthratio are particularly suitable, for example, for side radiation forbacklighting or as light sources in LED filaments to replace thefilament in a light bulb. However, efficient operation of thesemiconductor chips requires good current distribution in the lateraldirection. For conventional semiconductor chips with metallic contactstructures or transparent conductive layers, this leads to limitationswith regard to achievable geometries.

It could therefore be helpful to provide a radiation-emittingsemiconductor chip characterized by a high efficiency largelyindependent of its geometric shape.

SUMMARY

We provide a radiation-emitting semiconductor chip comprising asemiconductor body having an active region that generates radiation; afirst contact layer having a first contact surface for externalelectrical contacting of the semiconductor chip and a first contact webstructure connected to the first contact surface; a second contact layerhaving a second contact surface for external electrical contacting ofthe semiconductor chip and a second contact web structure connected tothe second contact surface, wherein the first contact web structure andthe second contact web structure overlap in places in plan view of thesemiconductor chip; a current distribution layer through which the firstsemiconductor layer electrically conductively connects to the firstcontact layer; and an insulation layer containing a dielectric material,wherein the insulation layer is arranged between the first semiconductorlayer and the current distribution layer and has a plurality of openingsinto which the current distribution layer extends, and a diameter of theopenings is 1 μm to 20 μm.

We also provide a radiation-emitting semiconductor chip comprising asemiconductor body having an active region that generates radiation; afirst contact layer having a first contact surface for externalelectrical contacting of the semiconductor chip and a first contact webstructure connected to the first contact surface; a second contact layerhaving a second contact surface for external electrical contacting ofthe semiconductor chip and a second contact web structure connected tothe second contact surface, wherein the first contact web structure andthe second contact web structure overlap in places in plan view of thesemiconductor chip; a current distribution layer through which the firstsemiconductor layer electrically conductively connects to the firstcontact layer; and an insulation layer containing a dielectric material,wherein the insulation layer is arranged between the first semiconductorlayer and the current distribution layer and has a plurality of openingsinto which the current distribution layer extends, and the insulationlayer is formed as a filter layer that predominantly transmits incidentradiation within a first angular range and predominantly reflectsincident radiation within a second angular range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C show an example of a radiation-emittingsemiconductor chip in schematic representation of a section of asectional view (FIG. 1A), in plan view (FIG. 1B) and in an enlargedrepresentation of a section of the sectional view in FIG. 1A (FIG. 1C).

FIGS. 2A and 2B each show an example of a radiation-emittingsemiconductor chip in a schematic cross-sectional view.

FIG. 3 shows an example of a radiation-emitting semiconductor chip inschematic plan view.

FIGS. 4A and 4B each show an example of a radiation-emittingsemiconductor chip in schematic plan view.

FIGS. 5A, 5B and 5C each show an example of a radiation-emittingsemiconductor chip in schematic plan view.

FIGS. 6A and 6B each show an example of a radiation-emittingsemiconductor chip in schematic plan view.

FIGS. 7A and 7B each show an example of a radiation-emittingsemiconductor chip in schematic plan view.

FIGS. 8A, 8B and 8C each show an example of a radiation-emittingsemiconductor chip in schematic plan view.

FIGS. 9A and 9B show an example of a radiation-emitting semiconductorchip (FIG. 9A) and a simulation result for a comparison structure (FIG.9B).

REFERENCE SIGN LIST

-   1 radiation-emitting semiconductor chip-   2 semiconductor body-   20 active region-   21 first semiconductor layer-   22 second semiconductor layer-   250 recess-   250 side surfaces-   28 radiation exit surface-   281 partial surfaces-   29 carrier-   3 first contact layer-   31 first contact surface-   34 connecting straight line-   345 center distance-   35 first contact web structure-   351 first contact web-   351 a further first contact web-   3510 longitudinal axis of the first contact web-   3511 transverse extent of the first contact web-   359 node of the first contact web structure-   4 second contact layer-   41 second contact surface-   42 contact-giving layer-   43 mirror layer-   44 barrier layer-   45 second contact web structure-   451 second contact web-   4510 longitudinal axis of the second contact web-   4511 transverse extent of the second contact web-   459 node of the second contact web structure-   51 current distribution layer-   52 connection layer-   6 insulation layer-   60 opening-   65 dielectric mirror layer-   650 cutout-   7 passivation layer-   8 arrow-   91 first contact structure-   92 second contact structure

DETAILED DESCRIPTION

We provide a radiation-emitting semiconductor chip comprising asemiconductor body. The semiconductor body has an active region thatgenerates radiation. For example, the active range is intended for thegeneration of radiation in the ultraviolet, visible or infrared spectralrange. In particular, the active region is arranged between a firstsemiconductor layer and a second semiconductor layer, wherein the firstsemiconductor layer and the second semiconductor layer are differentfrom one another at least in places with respect to their conductiontype so that the active region is located in a pn-junction. The firstsemiconductor layer, the second semiconductor layer and the activeregion can each be formed as a single-layer or a multi-layer.

The semiconductor chip may have a first contact layer. In particular,the first contact layer has a first contact surface for externalelectrical contacting of the semiconductor chip. For example, the firstcontact surface for electrical contacting of the first semiconductorlayer is provided. Furthermore, the first contact layer may have a firstcontact web structure connected to the first contact surface. The firstcontact web structure is intended for the lateral distribution of chargecarriers that are injected over the first contact surface duringoperation of the radiation-emitting semiconductor chip.

A lateral direction is a direction parallel to a main extension plane ofthe active region. Accordingly, a vertical direction is perpendicular tothe main extension plane of the active region.

The semiconductor chip may have a second contact layer comprising asecond contact surface for external electrical contacting of thesemiconductor chip. In particular, the second contact layer is intendedfor electrical contacting of the second semiconductor layer. Forexample, the second contact layer has a second contact web structureconnected to the second contact surface.

Expediently, there is no direct electrical contact between the firstcontact layer and the second contact layer. In particular, a currentpath runs between the first contact layer and the second contact layerthrough the semiconductor body, in particular through the active region.

The first contact web structure and the second contact web structure mayoverlap at least in places in plan view of the semiconductor chip. Areasin which the first contact web structure and the second contact webstructure overlap can be used both for lateral current distribution tocontact the first semiconductor layer and for lateral currentdistribution to contact the second semiconductor layer. For example, atleast 10%, at least 30% or at least 90% of the first contact webstructure is arranged within the second contact web structure in planview of the semiconductor chip. The larger this percentage is, the morearea of the semiconductor chip, which cannot be used for radiationgeneration anyway due to the second contact web structure, can also beused for charge carrier distribution over the first contact webstructure. Compared to a radiation-emitting semiconductor chip in whichthe first contact layer and the second contact layer are arranged nextto one another without overlapping, the area of the active regioncovered by the contact layers may be reduced. However, one of thecontact layers, for example, the first contact layer, may also have atleast one contact web that is free of overlaps with the other, forexample, the second contact layer. In contrast, the first contactsurface and the second contact surface are arranged without overlappingso that both contact surfaces are accessible for external electricalcontacting.

In particular, the first contact web structure may have a number ofcontact webs greater than or equal to the number of contact webs of thesecond contact web structure.

A contact web structure is generally understood to be a region of acontact layer that, compared to the contact surface intended forelectrical contacting, has a comparatively small extent at least in alateral direction. Alternatively or in addition, a contact web can, forexample, have a greater extent along a lateral direction than in aperpendicular direction thereto. For example, a contact web has alongitudinal axis, wherein a length of the longitudinal axis is at leasttwice as large, at least five times as large or at least ten times aslarge as a maximum transverse extent of the contact web perpendicular tothe longitudinal axis. The longitudinal axis can be straight, bent orcurved. A contact web structure may have one or more contact webs.

The semiconductor chip may have a current distribution layer. The firstsemiconductor layer connects to the first contact layer via the currentdistribution layer. For example, the current distribution layer directlyadjoins the first contact layer. For example, the first contact layer iscompletely arranged within the current distribution layer in plan viewof the semiconductor chip.

The semiconductor chip may have an insulation layer. The insulationlayer, for example, contains a dielectric material. The dielectricmaterial is an electrically weak or non-conductive, non-metallicmaterial, whose charge carriers are generally not freely movable, forexample, at the usual operating currents. The insulation layer contains,for example, at least one of the following materials: silicon nitride,silicon dioxide, silicon oxynitride, aluminum oxide, titanium oxide,tantalum oxide, and niobium oxide.

For example, the insulation layer covers at least 30%, about 50%, atleast 70% or at least 90% of the entire base area of the semiconductorchip in plan view. For example, the insulation layer covers a maximum of99% of the entire base area of the semiconductor chip in plan view.

The insulation layer may have a plurality of openings. The currentdistribution layer extends into the openings. In the production of thesemiconductor chip, the position of the openings can be used todetermine at which places the current injection on the semiconductorchip is greatest in plan view of the semiconductor chip.

For example, the openings are surrounded by the material of theinsulation layer along their entire circumference. For example, theopenings are at least partially or completely filled with material fromthe current distribution layer.

For example, with regard to their distribution density and/or size, theopenings are formed such that a uniform lateral current injection ispromoted in the semiconductor chip.

For example, a distance between two adjacent openings shall be 5 μm to60 μm, approximately 20 μm to 50 μm.

A diameter of the openings shall be in particular 0.5 μm to 20 μm, forexample, 2 μm to 6 μm. The diameter is the longest lateral extent in anon-round opening.

For example, a distribution density of the openings is preferably200,000 openings per mm² to 10 openings per mm², promoting a laterallyuniform and homogeneous current injection in the semiconductor chip.

The openings may also differ in shape and/or size from one another. Forexample, one or more openings can be provided at the edge of thesemiconductor chip that are larger than openings in the middle of thesemiconductor chip.

The radiation-emitting semiconductor chip may comprise a semiconductorbody having an active region that generates radiation. The semiconductorchip comprises a first contact layer having a first contact surface toelectrically contact the semiconductor chip and a first contact webstructure connected to the first contact surface. The semiconductor chipcomprises a second contact layer having a second contact surface forexternal electrical contacting of the semiconductor chip and a secondcontact web structure connected to the second contact surface, whereinthe first contact web structure and the second contact web structureoverlap in places in plan view of the semiconductor chip. Thesemiconductor chip comprises a current distribution layer, through whichthe first semiconductor layer electrically connects to the first contactlayer. The semiconductor chip comprises an insulation layer containing adielectric material, wherein the insulation layer is arranged betweenthe first semiconductor layer and the current distribution layer andhaving a plurality of openings, into which the current distributionlayer extends.

The semiconductor chip may have a connection layer. The connection layerelectrically connects to the first contact layer, for example, via thecurrent distribution layer. In particular, the connection layer directlyadjoins the semiconductor body, in particular the first semiconductorlayer. For example, the connection layer does not directly adjoin thefirst contact layer at any places.

For example, the insulation layer is arranged in places between theconnection layer and the current distribution layer, in particular inthe vertical direction. By the insulation layer, a direct verticalcurrent path between the connection layer and the current distributionlayer is at least partially prevented.

For example, the insulation layer is arranged vertically between thefirst contact layer and the second contact layer.

The connection layer and the current distribution layer connect to oneanother, expediently, in an electrically conductive manner in the regionof the openings. The openings thus define, at which place the currentdistribution layer electrically conductively connects to the connectionlayer. For example, the connection layer and the current distributionlayer adjoin one another in the openings.

In particular, the openings may be the only places where the connectionlayer and the current distribution layer are adjacent to one another.

The radiation-emitting semiconductor chip may have a length to widthratio of at least 4:1 or at least 6:1. For example, the length-to-widthratio is at least 8:1, at least 15:1, or at least 20:1. For example, thelength-to-width ratio is at most 100:1 or at most 50:1. Semiconductorchips with such a length-to-width ratio are particularly suitable, forexample, for lateral coupling into a flat light guide, e.g.,backlighting a liquid crystal display, or as a light source in an LEDfilament.

With a right-angled radiation-emitting semiconductor chip, the extentalong the longest edge is regarded as the length. In another polygonalsemiconductor chip or one at least partially curved in plan view, thelength is considered to be the extent along the direction along whichthe extent is greatest. In this example, the width is given by themaximum extent perpendicular to the direction along which the length ismeasured.

With the conventional structure for radiation-emitting semiconductorchips, such a high length-to-width ratio cannot be achieved efficientlybecause the current density distribution is too inhomogeneous.Commercially available radiation-emitting semiconductor chips thereforehave a maximum length-to-width ratio of 3:1.

The first contact web structure and/or the second contact web structuremay be symmetrically formed, in particular symmetrically to a connectingstraight line through the first contact surface and the second contactsurface. For example, the first contact web structure and/or the secondcontact web structure is formed axially symmetrically to the connectingstraight line. The connecting straight line can in particular runthrough the center of area of the first contact surface and/or thesecond contact surface. The structure of the first contact surfaceand/or the second contact surface itself need not necessarily besymmetrical to the connecting straight line.

In a contact web structure with an odd number of contact webs, onecontact web in particular overlaps with the connecting straight line.

With an even number of contact webs, all contact webs can have at leastone partial surface arranged without overlap to the connecting straightline and which, for example, runs parallel to the connecting straightline.

A transverse extent of at least one contact web of the first contact webstructure and/or the second contact web structure may decrease withincreasing distance from the associated contact surface. The greater thedistance from the corresponding contact surface, the lower is therequired ampacity for the respective contact web. Such tapered, inparticular stacked, current webs can control the current flow in themetallic conductors.

The second contact web structure and the connecting straight linethrough the first contact surface and the second contact surface maydivide a radiation exit surface of the semiconductor body into aplurality of partial surfaces in which a size of the largest partialsurface is larger by at most 50%, for example, at most 25% or at most10%, than a size of the smallest partial surface. In particular, allpartial surfaces can be of the same size or essentially the same size.The radiation exit surface is a surface of the semiconductor bodyrunning parallel to the main extension plane of the active region andthrough which a part of the radiated radiation emerges during operationof the radiation-emitting semiconductor chip. For example, thesemiconductor chip has a carrier, wherein the semiconductor body isarranged on the carrier and the radiation exit surface is arranged onthe side of the semiconductor body facing away from the carrier.

An efficient current extension with a homogeneous current densitydistribution can be achieved particularly easily and reliably if theresulting partial surfaces of the radiation exit surface differ aslittle as possible from one another. For example, the second contact webstructure and the connecting straight line divide the radiation exitsurface into at least four partial surfaces.

In particular, the number of contact webs and the number of formedpartial surfaces can be selected as a function of the extent of theradiation-emitting semiconductor chip in the lateral direction, inparticular as a function of its width.

The first contact web structure and/or the second contact web structuremay have a node from which at least three contact webs branch off. Inparticular, the first contact surface and/or the second contact surfaceform the node. In other words, the contact surfaces may be formed inplaces where there is already a comparatively large amount of materialfor the first contact layer and/or the second contact layer. Theadditional material coverage of the radiation exit surface required forthe formation of the first contact surface and/or the second contactsurface is thus minimized. Overall, the total area required for thefirst contact layer and/or the second contact layer can be minimizedwith same good current extent and external electrical contactability viathe contact surfaces.

An electrical surface resistance of the current distribution layer mayat most be three times or at most twice as large as an electricalsurface resistance of the second semiconductor layer. For example, theelectrical sheet resistance of the current distribution layer is at most50%, at most 20% or at most 10% higher than the electrical sheetresistance of the second semiconductor layer. The sheet resistance istypically given in Ω/□ and calculated from the specific resistance ofthe material used and the layer thickness. The smaller the differencesin electrical sheet resistance, the more uniform is the injection ofcharge carriers from opposite sides into the active region.

A center distance between the first contact surface and the secondcontact surface may be at least one fifth of the length of thesemiconductor chip. This applies in particular to when at least part ofthe first contact web structure is further away from the second contactsurface than the first contact surface or vice versa.

At least one contact web may extend from the first contact surface in adirection away from the second contact surface or vice versa. Inparticular, the contact web may extend in the opposite direction.

The insulation layer may cover at least 30% of the area of theconnection layer. For example, the insulation layer covers at least 50%,at least 70% or at least 90% of the connection layer. The insulationlayer can therefore cover a large area of the connection layer. Forexample, the insulation layer covers the connection layer by a maximumof 95% or 99%.

The insulation layer may be formed as a filter layer that predominantlytransmits incident radiation within a first angular range andpredominantly reflects incident radiation within a second angular range.“Predominantly” means in particular that at least 60% of the radiationis transmitted or reflected.

In particular, the angles of the first angular range relative to thevertical direction are smaller than the angles of the second angularrange. Radiation incident on the insulation layer at comparatively steepangles is therefore predominantly transmitted, while radiation incidentat comparatively flat angles is predominantly reflected. Radiationcomponents that could not be coupled out from the semiconductor chipanyway due to a comparatively flat course are therefore already retainedat the insulation layer. Radiation absorption losses in layersdownstream of the insulation layer, for example, in the currentdistribution layer, can thus be reduced.

For example, the boundary between the first angular range and the secondangular range is determined by the critical angle of total reflectionthat can be derived from the refractive index of the semiconductor bodyand the refractive index of the surrounding medium. The first angularrange includes angles smaller than this limit. The second angular range,on the other hand, includes angles that are larger than this limit.

The insulation layer that in particular is formed as a filter layer canconsist of a single layer. This means in particular that the insulationlayer is homogeneous and, for example, made of a single dielectricmaterial. The dielectric material has the advantage of an adaptedrefractive index, where “adapted” means that the refractive index of thedielectric material is greater than or equal to the refractive index ofa medium surrounding the insulation layer. The surrounding medium issubordinated to the insulation layer starting from the semiconductorbody. The surrounding medium comprises elements that enclose thesemiconductor body and in particular have a protective function. Forexample, the semiconductor body can have a passivation layer and/orencapsulation as the surrounding medium.

Alternatively, the insulation layer formed in particular as a filterlayer, is multi-layered and has at least two sublayers that differ fromone another in their refractive index. Preferably, the filter layercomprises a layer sequence of alternating sublayers with higherrefractive index and lower refractive index. In particular, thesublayers with a higher refractive index have a lower thickness than thesublayers with a lower refractive index.

Preferably, the insulation layer formed in particular as a filter layerhas a thickness of 400 nm to 800 nm. When dimensioning the thickness ofthe insulation layer, care must be taken on the one hand to limit theproduction effort, which is greater with a multi-layer structure of theinsulation layer than with a single-layer structure and, on the otherhand, to achieve the desired filter characteristic that can be betterachieved with a multi-layer structure than with a single-layerstructure. With a thickness of 400 nm to 800 nm, a suitable compromisebetween manufacturing effort and filter characteristics can be achieved.

The insulation layer may be adjacent to the connection layer and thecurrent distribution layer. Between the connection layer and the currentdistribution layer there are no other layers in the vertical directionapart from the insulation layer, at least in places. In other words, theinsulation layer is at least in places the only layer arranged betweenthe connection layer and the current distribution layer.

The connection layer may have a smaller thickness than the currentdistribution layer. For example, the current distribution layer is atleast twice as thick as the connection layer. For example, a thicknessof the connection layer shall be 3 nm to 30 nm, approximately 5 nm to 25nm. For example, a thickness of the current distribution layer is 30 nmto 200 nm, approximately 50 nm to 150 nm. In particular due to thegreater thickness, the current distribution layer is characterized by agreater transverse conductivity than the connection layer. In contrast,the connection layer also has lower absorption losses for the radiationpassing through the connection layer due to its lower thickness.

Radiation absorption losses in the current distribution layer can bereduced by the insulation layer that acts in particular as a filterlayer. In other words, the combination of a connection layer and acurrent distribution layer and, in particular, an insulation layerarranged in places in the vertical direction between them, a hightransverse conductivity with low absorption losses at the same time isachieved.

At least 50% of the total area of the second contact web structure mayoverlap the first contact web structure. In other words, at least halfof the area covered by the second contact web structure is also used forcurrent distribution via the first contact web structure.

The semiconductor body may have at least one recess extending from theradiation exit surface through the active region. In particular, thesecond contact layer electrically connects to the semiconductor body inthe recess. For example, the second contact layer directly adjoins thesemiconductor body, in particular the second semiconductor layer. Forexample, material of the insulation layer and/or material of the currentdistribution layer is arranged at least in places in the recess.

However, the recess can also be completely filled with material from thesecond contact layer.

The insulation layer may be arranged between the first contact layer andthe second contact layer. The insulation layer also serves as anelectrical separation between the first and second contact layers sothat there is no direct current path between these contact layers.

There may be no direct vertical current path between the first contactlayer and the semiconductor body at any place of the semiconductor chip.A charge carrier injection from the first contact layer into thesemiconductor body is therefore not carried out directly below the firstcontact layer, but at a distance from it in the lateral direction. Thisreduces the amount of radiation generated in the active region directlybelow the first contact layer and prevented from escaping by the firstcontact layer.

A dielectric mirror layer may be arranged in places between thesemiconductor body and the current distribution layer. For example, thedielectric mirror layer comprises a plurality of layer pairs, the layersof the layer pairs being different from one another with respect totheir refractive indices. For example, the dielectric mirror layer hasbetween and including three and including ten sublayers, whereinadjacent sublayers differing in their refractive index from one another.Preferably, the dielectric mirror layer comprises a layer sequence ofalternating sublayers with higher refractive index and lower refractiveindex. In particular, the sublayers with a higher refractive index havea lower thickness than the sublayers with a lower refractive index.

In particular, the dielectric mirror layer is intended to avoidabsorption losses at the first and/or second contact layer.

The dielectric mirror layer particularly covers the side surfaces of therecesses in places. For example, the dielectric mirror layer is arrangedvertically in places between the connection layer and the currentdistribution layer, in particular between the connection layer and theinsulation layer. This prevents radiation from escaping from thesemiconductor body at the side surface of the recess and subsequentlycausing absorption losses at the first contact layer and/or the secondcontact layer.

The dielectric mirror layer may overlap in places with the first contactlayer and the second contact layer in plan view of the semiconductorchip. Radiation absorption can thus be avoided or at least reduced bothat the first contact layer and at the second contact layer.

The connection layer and/or the current distribution layer may contain aTCO material.

Transparent conductive oxides (TCO) are transparent conductivematerials, usually metal oxides such as zinc oxide, tin oxide, cadmiumoxide, titanium oxide, indium oxide or indium tin oxide (ITO). Inaddition to binary metal oxygen compounds such as ZnO, SnO₂ or In₂O₃,ternary metal oxygen compounds such as Zn₂SnO₄, CdSnO₃, ZnSnO₃, MgIn₂O₄,GaInO₃, Zn₂In₂O₅ or In₄Sn₃O₁₂ or mixtures of different transparentconducting oxides also belong to the group of TCOs. Furthermore, theTCOs do not necessarily correspond to a stoichiometric composition andcan also be p- or n-doped.

The connection layer and the current distribution layer can be made ofthe same material. Alternatively, the connection layer and the currentdistribution layer can also have material compositions different fromone another. For example, the contact layer may be selected for goodcontact resistance to the semiconductor body and/or the currentdistribution layer for high transmission of radiation generated in theactive region.

The dielectric mirror layer may be arranged in places between thesemiconductor body and the second contact layer. For example, thedielectric mirror layer has a cutout in which the second contact layerdirectly adjoins the semiconductor body. By the dielectric mirror layer,it can be avoided, at least in places, that radiation generated in theactive region is absorbed by the second contact layer.

The second contact layer may have a mirror layer. For example, silver oraluminum is suitable for the mirror layer. Silver can be used to achieveparticularly high reflectivities in the visible spectral range. Forexample, the mirror layer has a thickness of 300 nm to 2 μm.

The second contact layer may have a contact-giving layer. Thecontact-giving is intended to establish a good ohmic contact to thesemiconductor body, in particular to the second semiconductor layer. Forexample, the contact-giving has a thickness of 3 nm to 100 nm. Thecontact-giving is arranged in particular between the mirror layer andthe second semiconductor layer. A material that in itself would form acomparatively poor contact with the semiconductor body such as silver ton-type nitride compound semiconductor material, is also suitable for themirror layer. For example, the contact-giving layer contains a TCOmaterial such as ITO or ZnO. In particular with a TCO material for thecontact-giving layer and silver for the mirror layer, a contact layercan be realized, which is characterized by a high reflectivity and atthe same time a good electrical contact to the second semiconductorlayer.

The second contact layer may have a barrier layer. In particular, themirror layer is arranged between the contact-giving layer and thebarrier layer. For example, a metal such as Ti, Pt, Cu or Au or a TCOmaterial such as ITO or ZnO is suitable as a barrier layer. For example,the barrier layer has a thickness of 30 nm to 400 nm. The mirror layercan be encapsulated by the barrier layer. A material with a risk ofmigration, for example, due to moisture is therefore also suitable forthe mirror layer.

The mentioned materials and/or at least one or all layers can also beused for the first contact layer.

In particular, the following effects can be achieved with theradiation-emitting semiconductor chip described.

The regions are reduced in which a metal layer such as the first contactlayer or the second contact layer is directly adjacent to thesemiconductor chip. This increases the brightness of theradiation-emitting semiconductor chip at the same operating current.

The insulation layer reduces absorption losses, in particular in thecurrent distribution layer. Even when a comparatively thick currentdistribution layer is used with regard to high transverse conductivityor low surface resistance, absorption losses are reduced by theinsulation layer. In particular, the insulation layer can fulfil thefunction of an angle-selective filter layer.

The regions in which the highest current density occurs during operationof the semiconductor chip can be adjusted by at least one opening in theinsulation layer. In particular, these regions can be laterally spacedfrom the first contact layer. For example, the areas where the highestcurrent density occurs can also be laterally spaced from the firstcontact web structure.

As a result, the amount of light generated in the active regionincreases and the loss of efficiency at high operating currents (alsoknown as “droop”) is reduced. A higher current density distribution anda resulting homogeneous light distribution on the radiation exit surfaceof the semiconductor chip also increases the efficiency of a downstreamarranged radiation conversion material that further increases thebrightness of a component with such a radiation-emitting semiconductorchip.

All in all, there is great freedom with regard to the geometry of thesemiconductor chip. In particular, efficient semiconductor chips with alarge area of the radiation exit surface and/or a particularly largelength-to-width ratio can also be realized. The length of thesemiconductor chip is limited only by the current distribution in thetypically metallic conductors, i.e., the first and second contactlayers. The ampacity and the current distribution can be increased byincreasing the cross-section of these contact layers, in particular inthe region of the contact web structures so that almost any scaling ofthe semiconductor chip is possible. At the same time, a more homogeneouscurrent density distribution can be achieved in the active region, inparticular by positioning and dimensioning the openings.

The efficiency of the semiconductor chip can be further increased by thespatial structure of the contact web structures, in particular adaptedto the dimensioning of the semiconductor chip.

Furthermore, absorption losses at the second contact layer can also beavoided, for example, by the dielectric mirror layer. By an arrangementof the dielectric mirror layer on a side surface of the semiconductorchip, for example, on the side surface of the recess, absorption losseson the second contact layer can be further avoided or at least reduced.

The second contact layer itself can be characterized by particularly lowabsorption losses, in particular by a multi-layer structure with acontact-giving and a mirror layer. Migration effects can be suppressedby the barrier layer so that the freedom in the choice of material forthe mirror layer is increased.

Further examples and expediencies result from the following descriptionof the examples in connection with the figures.

Same, similar or seemingly similar elements are provided in the figureswith the same reference signs.

The figures are schematic representations and therefore not necessarilytrue to scale. Rather, comparatively small elements and, in particular,layer thicknesses can be displayed exaggeratedly large forclarification.

FIGS. 1A, 1B and 1C show an example of a radiation-emittingsemiconductor chip 1, where FIG. 1A shows a section of the semiconductorchip in sectional view along the line AA′ shown in the plan view in FIG.1B.

The radiation-emitting semiconductor chip 1 has a semiconductor body 2with a semiconductor layer sequence. The semiconductor body 2 inparticular comprises an active region 20 that generates radiation and isarranged between a first semiconductor layer 21 of a first conductiontype (for example, p-conducting) and a second semiconductor layer 22 ofa second conduction type (for example, n-conducting) different from thefirst conduction type. The semiconductor body 2, in particular theactive region 20, is preferably based on an III-V compound semiconductormaterial, in particular a nitride compound semiconductor material.

“Based on nitride compound semiconductor material” means that at leastone layer of the semiconductor regions comprises a nitride III/Vcompound semiconductor material, preferably Al_(n)Ga_(m)In_(1-n-m)N,wherein 0≤n≤1, 0≤m≤1 and n+m≤1. Thereby, this material does notnecessarily have to have a mathematically exact composition according tothe above formula. Rather, it may contain one or more dopants andadditional components that essentially do not alter the characteristicphysical properties of the Al_(n)Ga_(m)In_(1-n-m)N material. Forsimplicity's sake, however, the above formula contains only theessential components of the crystal lattice (Al, Ga, In, N), even ifthese may be partially replaced by small amounts of other substances.

The semiconductor body 2 is arranged on a carrier 29. In particular, thecarrier is a growth substrate for the semiconductor layer sequence ofthe semiconductor body. For a semiconductor body based on nitridecompound semiconductor material, sapphire, silicon carbide or galliumnitride are suitable as growth substrates.

A first contact layer 3 and a second contact layer 4 are arranged on aradiation exit surface 28 facing away from the carrier 29. The firstcontact layer 3 has a first contact surface 31 for the externalelectrical contacting of the first semiconductor layer 21. The secondcontact layer 4 has a second contact surface 41 intended for theexternal electrical contacting of the second semiconductor layer.

The first contact layer 3 also has a first contact web structure 35connected to the first contact surface 31. Accordingly, the secondcontact layer 4 has a second contact web structure 45 electricallyconductively connected to the second contact surface 41.

In the example shown in FIG. 1B, the first contact web structure 35comprises a first contact web 351 and the second contact web structure451 comprises a second contact web 451 that emanate from the associatedfirst contact surface 31 and second contact surface 41, respectively.The shape and number of contact webs can be varied within wide limits.This is explained in more detail in FIGS. 3 to 8C. The number of contactwebs of the first contact web structure 35 and the second contact webstructure 45 may also be different. For example, the number of contactwebs of the first contact web structure is greater than the number ofcontact webs of the second contact web structure.

The first contact web structure 35 and the second contact web structure45 overlap in plan view on the radiation-emitting semiconductor chip. Inthis way, areas of the semiconductor chip in which the active region 20is already removed for formation of the second contact web structure 45can also be used for current distribution for electrical contacting ofthe first semiconductor layer 21.

Deviating from the example described, the first contact web structure 35and the second contact web structure 45 can overlap to a smallerpercentage. For example, the first contact web structure 35 may have atleast one contact web that does not overlap with the second contact webstructure 45 by at least half of its main axis of extension.

The second contact layer 4, in particular the second contact webstructure 45, adjoins the second semiconductor layer 22 in a recess 25of the semiconductor body. By the recess, the second semiconductor layer22 covered by the first semiconductor layer 21 is exposed in places forcontacting with the second contact layer 4.

An insulation layer 6 is arranged between the first contact layer 3 andthe second contact layer 4 in the vertical direction. The insulationlayer 6 covers the radiation exit surface 28 of the semiconductor body 2in some places. In the example shown, the insulation layer 6 also coversthe side surfaces 250 of the recesses 25.

The semiconductor chip 1 also comprises a current distribution layer 51that is electrically conductively connects to the first contact layer 3.The first semiconductor layer 21 electrically connects to the firstcontact layer 3 via the current distribution layer 51.

Furthermore, the radiation-emitting semiconductor chip 1 comprises aconnection layer 52. The connection layer 52 electrically conductivelyconnects to the first contact layer via the current distribution layer51. Between the current distribution layer 51 and the connection layer52 the insulation layer 6 is arranged in places, in particular seen invertical direction.

Insulation layer 6 has a plurality of openings 60 in which the currentdistribution layer 51 and the connection layer 52 are adjacent to oneanother. During operation of the radiation-emitting semiconductor chip,the current density injected into the semiconductor chip is highest in aregion vertically below the openings 60. The openings in the insulationlayer 6 can therefore be used to define the regions in which the currentdensity is highest. Without an insulation layer between the currentdistribution layer 51 and the first semiconductor layer, in particularbetween the current distribution layer and the connection layer 52,which may be present, the current density would be highest in the regionaround the first contact layer 3. In lateral regions further away fromthe first contact layer 3, however, only a comparatively small chargecarrier injection would occur. A further lateral current distributioncan take place from the openings via the connection layer 52.

The openings 60 are arranged in lateral direction such that in lateraldirection a homogeneous current density distribution is achieved. Inparticular, the arrangement of the openings on the radiation exitsurface 28 is also selected on the basis of the respective materialparameters of the current distribution layer 51 and the connection layer52 such that the current density distribution is as homogeneous aspossible. For example, the density, size or position of the openings canbe varied, in particular depending on the geometric shape of thesemiconductor chip and the structure of the first contact web structure35 and the second contact web structure 45. In FIG. 1B only the twoopenings 60 arranged in the region of the sectional view of FIG. 1A areshown explicitly for simplified representation.

For example, edge regions of the radiation exit surface 28 can beprovided with more openings than central regions of the radiation exitsurface. The distances between the openings may be 20 μm to 50 μm. Asuitable diameter of the openings shall be in particular 1 μm to 15 μm,approximately 2 μm to 6 μm.

Despite the openings 60, the insulation layer 6 can cover a large areaof the connection layer such as at least 30%, at least 50% or at least70% of the area of the connection layer in plan view of thesemiconductor chip. For example, the insulation layer does not covermore than 90% or 95% of the connection layer 52.

The connection layer 52 is less thick than the current distributionlayer 51. Unlike the current distribution layer 51, the connection layer52 does not have to have a high transverse conductivity. Due to thecomparatively small thickness of the connection layer 52, absorptionlosses in the connection layer can be reduced.

As seen from the active region 20, the insulation layer 6 is arranged infront of the current distribution layer 51 at least in places. Inparticular, the insulation layer 6 can fulfill the function of a filterlayer, wherein the filter layer has a higher reflectivity for radiationat comparatively large angles to the normal to the main extension planeof the active region 20 than for radiation at a comparatively smallangles to the normal. As a result, radiation components that could notescape from semiconductor chip 1 anyway due to total reflection canalready be reflected largely loss-free at the insulation layer 6.Absorption losses in the current distribution layer 51 can thus bereduced. For example, the insulation layer can cover at least 50%, about70% or at least 90% of the entire base area of the semiconductor chip inplan view. Absorption losses can thus be avoided particularlyefficiently by the insulation layer 6.

In particular, for radiation in a first angular range, the transmissioncan be increased compared to a conventional semiconductor chip. Thefirst angular range refers to angles α with 0°≤α≤α_(tot), whereinα_(tot) is the critical angle of total reflection. At angles α that arelarger than the critical angle α_(tot), i.e., in a second angular rangewith α_(tot)≤α≤90°, absorption of the described semiconductor chip isconsiderably reduced compared to a conventional semiconductor chip. Thefirst angular range represents a conical area with a main axis parallelto the vertical direction. The critical angle of the total reflectionα_(tot) is determined from the refractive index of the semiconductorbody 2 and the refractive index of the surrounding medium, wherein, forexample, a critical angle α_(tot)=arcsin(1.55/2.5)=38.3° is obtained fora semiconductor body 2 formed from GaN with a refractive index n=2.5 andan surrounding medium with a refractive index n=1.55.

A particularly efficient filter effect can be achieved by a multi-layerstructure of the insulation layer with an alternating arrangement oflayers with a lower and higher refractive index. However, a filtereffect can also be achieved with a single-layer insulation layer.

An electrical sheet resistance of the current distribution layer 51 ispreferably at most three times or at most twice as large as anelectrical sheet resistance of the second semiconductor layer 22. Inparticular, the electrical sheet resistance of the current distributionlayer 51 is at most 50% or at most 20% higher than the electrical sheetresistance of the second semiconductor layer. The current distributionon the n-side, i.e., on the second semiconductor layer 22, and on thep-side, i.e., on the first semiconductor layer 21, is preferably assymmetrical as possible.

For example, an electrical sheet resistance of the current distributionlayer 51 is 8Ω/□ to 45Ω/□ has a maximum of 15Ω/□ or 10Ω/□. Such lowelectrical resistances of the current distribution layer 51 can berealized by a comparatively high thickness of the current distributionlayer 51. In particular, the insulation layer 6 described in connectionwith FIG. 1A can also be used to achieve a comparatively large layerthickness for the current distribution layer 51 and thus a lowelectrical surface resistance without suffering excessive absorptionlosses.

On the side facing away from the carrier 29, the radiation-emittingsemiconductor chip 1 can be closed in places by a passivation layer 7.The passivation layer serves in particular to protect the semiconductorbody from external stresses such as moisture, dust or mechanical stress.

The current distribution layer 51 and the connection layer 52 may eachbe formed from the same material or have different materials from oneanother. Preferably, the current distribution layer and the connectionlayer contain a TCO material such as ITO.

The first contact layer 3 and the second contact layer 4 or at least apartial layer thereof can each be formed metallic. This simplifiesexternal electrical contacting of the semiconductor chip 1.

A possible multilayer design of the second contact layer 4 is shownschematically in FIG. 1C.

The second contact layer consists of a contact-giving layer 42, a mirrorlayer 43 and a barrier layer 44.

For example, silver or aluminum is suitable for the mirror layer. Silvercan be used to achieve particularly high reflectivities in the visiblespectral range. For example, the mirror layer has a thickness of 300 nmto 2 μm.

A good ohmic contact to the semiconductor body can be formed by thecontact-giving layer 42, in particular also when using a material forthe mirror layer 43, which in itself would form a comparatively badcontact to the semiconductor body such as silver to n-conducting nitridecompound semiconductor material. For example, the contact-giving layerhas a thickness of 3 nm to 100 nm. The contact-giving layer is arrangedin particular between the mirror layer and the second semiconductorlayer. For example, the contact-giving layer contains a TCO materialsuch as ITO or ZnO. In particular with a TCO material for thecontact-giving layer and silver for the mirror layer, the second contactlayer 4 can be characterized by a high reflectivity and at the same timea good electrical contact to the second semiconductor layer.

A metal such as Ti, Pt, Cu or Au or a TCO material such as ITO or ZnO issuitable for the barrier layer 44. For example, the barrier layer has athickness of 30 nm to 400 nm. The barrier layer can be used toencapsulate the mirror layer 43. A material with a risk of migration,for example, due to moisture is therefore also suitable for the mirrorlayer, in particular silver.

The first contact layer 3 can also be formed multi-layered and have atleast one of the materials described in connection with the secondcontact layer.

In FIG. 1B, the first contact web structure 35 has exactly one firstcontact web 351. The second contact web structure 45 has exactly onesecond contact web 451. The first contact web structure 35 extendscompletely within the second contact web structure 45 in a plan view ofthe radiation-emitting semiconductor chip.

The first contact surface 31 and the second contact surface 41 differfrom one another with regard to their basic geometric shape so that thepolarity of the semiconductor device can be easily recognized opticallyby the basic shape of the contact surfaces. For example, the firstcontact surface is 31 circular and the second contact surface 41 squareor vice versa. Such a polarity marking can, however, also be in anotherform or omitted.

The first contact web 351 has a longitudinal axis 3510. Vertically tothe longitudinal axis, the first contact web 351 has a transverse extent3511. In the example shown, the transverse extent 3511 is constant overthe length of the longitudinal axis 3510 of the first contact web.

Accordingly, the second contact web 451 has a longitudinal axis 4510 anda transverse extent 4511 perpendicular to the longitudinal axis.

In plan view of the radiation-emitting semiconductor chip 1, the firstcontact web structure 35 extends completely within the second contactweb structure 45. Thus, regions of the radiation-emitting semiconductorchip that cannot anyway be used for radiation generation due to theactive region 20 removed for the structure of the second contactstructure, are also used at least partially for the first contact webstructure 35 so that no further shading of a radiation exit surface 28of the semiconductor body 2 is required for to form the first contactweb structure 35.

The longitudinal axis of the first contact web 3510 and the longitudinalaxis of the second contact web 4510 run congruently along a connectingstraight line 34, which runs through the first contact surface 31 andthe second contact surface 41, in particular through their center ofarea.

The first contact web structure 35 and the second contact web structure45 are formed axially symmetrically with respect to the connectingstraight line 34.

The semiconductor chip shown in FIG. 1B has an exemplary length-to-widthratio of about 14:1. Due to the described overlapping arrangement of thecontact web structures, in particular in connection with the openings 60in the insulation layer 6, almost any length-to-width ratios can beachieved, in particular length-to-width ratios of at least 8:1, at least15:1 or at least 20:1.

The number of contact webs of the first contact web structure 35 and/orthe second contact web structure 45 can be selected in particulardepending on the area of the radiation-emitting semiconductor chip andthe length-to-width ratio.

For example, the radiation-emitting semiconductor chip has one contactweb at a length-to-width ratio of 1:1 to 20:1 and an area of 0.05 to 0.5mm². For example, for an area of 0.25 to 0.5 mm² and a length-to-widthratio of 1:1 to 5:1, the number of contact webs is 2; for an area of thesemiconductor chip of 0.5 to 1.2 mm² and a length-to-width ratio of 1:1to 2:1, the number of contact webs is 3. For example, if the area of thesemiconductor chip is 1.2 to 2 mm² and the length-to-width ratio is 1:1to 2:1, the number of contact webs is 4; if the area of thesemiconductor chip is more than 2 mm² and the length-to-width ratio is1:1 to 2:1, the number of contact webs is 5 or more.

The first contact surface 31 and/or the second contact surface 42 neednot necessarily be formed symmetrically to the axis of symmetry. Forexample, the axis of symmetry can run through the second contact surface41 while the first contact surface 31 is displaced transverse to theaxis of symmetry, or vice versa.

The second example shown in FIG. 2A essentially corresponds to the firstexample described in connection with FIGS. 1A, 1B and 1C.

In contrast, the radiation-emitting semiconductor chip 1 also has adielectric mirror layer 65. The dielectric mirror layer 65 is arrangedin places between the semiconductor body 2 and the first contact layer3. In particular, the dielectric mirror layer 65 overlaps with the firstcontact layer 3 and the second contact layer 4. The dielectric mirrorlayer 65 has a cutout 650, in which the second contact layer 4 adjoinsthe semiconductor body 2, in particular the second semiconductor layer22. The dielectric mirror layer 65, for example, has a plurality oflayer pairs, with the layers of a layer pair each having differentrefractive indices from one another. The materials specified for theinsulation layer in the general part of the description are particularlysuitable for the dielectric mirror layer. The individual sublayers ofthe dielectric mirror layer are not explicitly shown for simplifiedrepresentation.

By the dielectric mirror layer 65 a radiation absorption at the secondcontact layer 4 can be avoided. This is illustrated by an arrow 8 thatindicates radiation reflected at the dielectric mirror layer 65.Furthermore, the dielectric mirror layer 65 also covers the side surface250 of the recess 25. This prevents radiation escaping through this sidesurface from being absorbed at the first contact layer 3 or at thesecond contact layer 4.

In particular, the dielectric mirror layer is arranged in regionsbetween the insulation layer 6 and the semiconductor body 2.Furthermore, the dielectric mirror layer 65 runs in places in a verticaldirection between the current distribution layer 51 and the connectionlayer 52. Deviating from this, the dielectric mirror layer 65 and theconnection layer 52 can also be arranged without overlapping. Thecurrent distribution layer 51 can completely cover the dielectric mirrorlayer 65 in plan view of the semiconductor chip.

The example shown in FIG. 2B is essentially the same as the secondexample described in FIG. 2A.

In contrast, the recess 25 is completely or at least almost completelyfilled with material of the dielectric mirror layer 65 and the secondcontact layer 4. In this example, the electrical contacting of thesecond semiconductor layer 22 is carried out via adjacent cutouts 650 ofthe dielectric mirror layer 65.

Preferably, the lateral extension of the cutouts 650 is also limitedalong a lateral main extension direction of the associated contact webof the second contact web structure 45. The cutouts are thus surroundedalong their entire circumference by material of the dielectric mirrorlayer. In other words, the second contact web structure 45 may becompletely underlaid with material of the dielectric mirror layer atleast at some places along the main extension direction of theassociated contact web in a lateral transverse direction to the mainextension direction of the contact web. Radiation absorption losses atthe second contact layer 4 can thus be further reduced.

Furthermore, FIG. 2B shows a passivation layer 7 on the side of thesemiconductor body 2 facing away from the carrier 29. This passivationlayer can also be used in the example shown in FIGS. 1A and 2A.

In the lateral direction, the contact finger of the first contact webstructure 35 overlapping with the recess 25 has a smaller lateral extentthan the associated contact finger of the second contact web structure45. Absorption losses at the second contact web structure can thus befurther reduced.

In the following examples, plan views are shown that in particular showthe course of the first contact web structure 35 and the second contactweb structure 45. In a sectional view, the following examples can beformed in particular as described in connection with FIG. 1A, 2A or 2B.The position of the openings 60 is not shown in the following figuresfor simplified representation. These can be formed and/or arranged asdescribed in FIG. 1B.

The example shown in FIG. 3 essentially corresponds to the exampledescribed in connection with FIGS. 1A to 1C. In contrast, the transverseextent 3511 of the first contact web 351 decreases with increasingdistance from the first contact surface 31. Accordingly, the transverseextent 4511 of the second contact web 451 decreases with increasingdistance from the second contact surface 41. The current flow in themetallic conductors, i.e., in the first contact web structure 35 and thesecond contact web structure 45, is controlled by the respectivelytapering stacked current webs. In particular, the cross section of thecontact webs is highest at the places where the current through thecontact webs is highest.

The first contact surface 31 and the second contact surface 41 do notnecessarily each have to be arranged at the edge of theradiation-emitting semiconductor chip 1.

This is illustrated by FIGS. 4A and 4B. In the example shown in FIG. 4,the first contact web structure 35 has a further first contact web 351 aextending from the first contact surface 31 in a direction away from thesecond contact surface 41. Part of the first contact web structure 35 istherefore further away from the second contact surface 41 than the firstcontact surface 31.

A center distance 345 between the first contact surface 31 and thesecond contact surface 41 is preferably at least one fifth of the extentof the radiation-emitting semiconductor chip along that direction.

The second contact web 451 continues over the first contact surface 31as seen from the second contact surface 41 so that the further firstcontact web 351 a bears on the second contact web 451 of the secondcontact web structure 451.

However, the structure of the radiation-emitting semiconductor chipdescribed above is also suitable for radiation-emitting semiconductorchips with a length-to-width ratio of 2:1 or less, in particular alsofor a length-to-width ratio of 1:1. FIG. 5A shows an example of asquared radiation-emitting semiconductor chip. The connecting straightline 34 between the first contact surface 31 and the second contactsurface 41 runs along a diagonal of the radiation-emitting semiconductorchip. Other basic forms of radiation-emitting semiconductor chips canalso be used such as hexagonal basic forms as shown in FIGS. 5B and 5C.With such a basic shape, there are several possibilities for positioningthe first contact surface 31 and the second contact surface 41. Forexample, as shown in FIG. 5C, the connecting straight line 34 can runthrough the corners of the hexagonal basic shape or through the edgecenter (FIG. 5B).

FIGS. 6A and 6B show two examples of a radiation-emitting semiconductorchip, with the first contact web structure 35 and the second contact webstructure 45 each having two first contact webs 351 and two secondcontact webs 451, respectively. The second contact web structure 45 andthe connecting straight line 34 divide a radiation exit surface 28 ofthe semiconductor body into partial surfaces 281. A size of the largestpartial surface is larger by at most 50%, preferably by at most 25% orby at most 10% than a size of the smallest partial surface. Inparticular, all partial surfaces can be of the same size or essentiallythe same size.

The first contact web structure 35 and the second contact web structure45 have a closed or at least largely closed basic form such as aframe-shaped basic form (FIG. 6A) or ring-shaped basic form (FIG. 6B).Such a configuration of the contact web structures is suitable, forexample, for radiation-emitting semiconductor chips with an area of 0.25to 0.5 mm² and a length-to-width ratio of 1:1 to 5:1.

The surfaces on both sides of the connecting straight line 34 forming anaxis of symmetry are thus the same or at least almost the same.Furthermore, the surfaces within the second contact web structure 45 andthe surfaces outside the second contact web structure 45 do not differor do not differ significantly.

Furthermore, as shown in FIG. 7A, the radiation-emitting semiconductorchip 1 may also have another polygonal, exemplarily triangular basicshape. For example, the contact webs of the contact web structures runparallel to the edges of the radiation-emitting semiconductor chip atleast in places or along their entire longitudinal axis. However, thisis not necessary. For example, FIG. 7B shows an example in which theradiation-emitting semiconductor chip 1 has a hexagonal basic shape,while the first contact web structure 35 and the contact web structure45 have an annular basic shape, i.e., a curved basic shape.

FIGS. 8A, 8B, and 8C show examples of radiation-emitting semiconductorchip structures where the first contact web structure 35 has a node 359and the second contact web structure 45 has a node 459. As seen from thenodes, three first contact webs 351 and three second contact webs 451extend away. The nodes 359, 459 are formed by the first contact surface31 and the second contact surface 41, respectively. The first contactsurface 31 and the second contact surface 41 are thus each formed atplaces where there is already a comparatively large material coveragewith material from the first contact layer or the second contact layer.All in all, this minimizes the material coverage of the radiation exitsurface with the material of the contact layers.

Simulation results of the lateral current density distribution for acomparison structure are shown in FIG. 9B, while FIG. 9A represents aradiation-emitting semiconductor chip 1 described above. In thesimulation results, regions of the semiconductor chip with high currentdensity are bright (slightly hatched) and regions with low currentdensity are dark (more strongly hatched).

In the comparison structure of a semiconductor chip shown in FIG. 9B, afirst contact structure 91 and a second contact structure 92 arearranged next to one another without overlapping. Only the first contactstructure 91 has contact webs that extend away from the contact surface.In the example shown, the current extent on the side of the secondcontact structure 92 has a limiting effect so that a current densitydrop occurs starting from the second contact structure 92. Therefore,there is no laterally homogeneous current injection. In particular, thecurrent injection on the side of the first contact structure facing awayfrom the second contact structure is very low compared to the regionaround the second contact structure, resulting in a highly inhomogeneousluminance distribution.

By the radiation-emitting semiconductor chip described, a particularlyhigh homogeneity of the current density distribution in the lateraldirection can be achieved. This increases the freedom to choose thegeometry of the semiconductor chip. In particular, semiconductor chipscan be realized that are characterized by a high homogeneity of thecurrent density distribution even with a length-to-width ratio that canbe scaled almost arbitrarily, for example, 4:1 or more.

The priority of DE 10 2017 129 783.9 is claimed, the subject matter ofwhich is hereby expressly incorporated by reference.

Our chips are not limited by the description of the examples. Rather,this disclosure includes any new feature and any combination of featuresthat in particular includes any combination of features in the appendedclaims, even the feature or combination itself is not explicitlymentioned in the claims or the examples.

The invention claimed is:
 1. A radiation-emitting semiconductor chipcomprising: a semiconductor body having an active region that generatesradiation; a first contact layer having a first contact surface forexternal electrical contacting of the semiconductor chip and a firstcontact web structure connected to the first contact surface, whereinthe first contact web structure is a region of the first contact layerthat, compared to the first contact surface, has a comparatively smallextent at least in a lateral direction; a second contact layer having asecond contact surface for external electrical contacting of thesemiconductor chip and a second contact web structure connected to thesecond contact surface, wherein 1) the first contact web structure andthe second contact web structure overlap in places in plan view of thesemiconductor chip, 2) the first contact layer, the second contact layerand a radiation exit surface are arranged at a same side on thesemiconductor body, 3) the first contact layer, the second contactlayer, the radiation exit surface and a radiation exit side of thesemiconductor chip are arranged at the same side of the semiconductorchip, and 4) the radiation is visible light, is produced in the activeregion and exits the semiconductor chip through the radiation exitsurface and the radiation exit side; a current distribution layerthrough which a first semiconductor layer electrically conductivelyconnects to the first contact layer; and an insulation layer containinga dielectric material, wherein the insulation layer is arranged betweenthe first semiconductor layer and the current distribution layer and hasa plurality of openings into which the current distribution layerextends, and a diameter of the openings is 1 μm to 20 μm.
 2. Theradiation-emitting semiconductor chip according to claim 1, wherein theradiation-emitting semiconductor chip has a length to width ratio of atleast 4:1.
 3. The radiation-emitting semiconductor chip according toclaim 1, wherein the radiation-emitting semiconductor chip has a lengthto width ratio of at least 6:1.
 4. The radiation-emitting semiconductorchip according to claim 1, wherein the first contact web structureand/or the second contact web structure is formed symmetrically to aconnecting straight line through the first contact surface and thesecond contact surface.
 5. The radiation-emitting semiconductor chipaccording to claim 1, wherein a transverse extent of at least onecontact web of the first contact web structure and/or the second contactweb structure decreases with increasing distance from the associatedcontact surface.
 6. The radiation-emitting semiconductor chip accordingto claim 1, wherein the second contact web structure and a connectingstraight line through the first contact surface and the second contactsurface divide a radiation exit surface of the semiconductor body into aplurality of partial surfaces, in which a size of the largest partialsurface is larger by at most 50% than a size of the smallest partialsurface.
 7. The radiation-emitting semiconductor chip according to claim1, wherein the first contact web structure and/or the second contact webstructure has a node from which at least three contact webs branch off,and the first contact surface and/or the second contact surface formsthe node.
 8. The radiation-emitting semiconductor chip according toclaim 1, wherein an electrical surface resistance of the currentdistribution layer is at most three times as large as an electricalsurface resistance of a second semiconductor layer.
 9. Theradiation-emitting semiconductor chip according to claim 1, wherein acenter distance between the first contact surface and the second contactsurface is at least ⅕ of the length of the semiconductor chip.
 10. Theradiation-emitting semiconductor chip according to claim 1, wherein atleast one contact web extends from the first contact surface in adirection away from the second contact surface or vice versa.
 11. Theradiation-emitting semiconductor chip according to claim 1, wherein theinsulation layer is formed as a filter layer that predominantlytransmits incident radiation within a first angular range andpredominantly reflects incident radiation within a second angular range.12. The radiation-emitting semiconductor chip according to claim 1,wherein the first contact surface and the second contact surface areaccessible for external electrical contacting from a radiation exitsurface of the semiconductor body.
 13. The radiation-emittingsemiconductor chip according to claim 1, wherein at least 50% of thetotal area of the second contact web structure overlaps the firstcontact web structure.
 14. The radiation-emitting semiconductor chipaccording to claim 1, wherein the insulation layer is arranged betweenthe first contact layer and the second contact layer.
 15. Theradiation-emitting semiconductor chip according to claim 1, whereinthere is at no place of the semiconductor chip a direct vertical currentpath between the first contact layer and the semiconductor body.
 16. Aradiation-emitting semiconductor chip comprising: a semiconductor bodyhaving an active region that generates radiation; a first contact layerhaving a first contact surface for external electrical contacting of thesemiconductor chip and a first contact web structure connected to thefirst contact surface; a second contact layer having a second contactsurface for external electrical contacting of the semiconductor chip anda second contact web structure connected to the second contact surface,wherein 1) the first contact web structure and the second contact webstructure overlap in places in plan view of the semiconductor chip,wherein 2) the first contact layer, the second contact layer and aradiation exit surface are arranged at a same side on the semiconductorbody, 3) the first contact layer, the second contact layer, theradiation exit surface and a radiation exit side of the semiconductorchip are arranged at the same side of the semiconductor chip, and 4) theradiation is visible light, is produced in the active region and exitsthe semiconductor chip through the radiation exit surface and theradiation exit side; a current distribution layer through which a firstsemiconductor layer electrically conductively connects to the firstcontact layer; and an insulation layer containing a dielectric material,wherein the insulation layer is arranged between the first semiconductorlayer and the current distribution layer and has a plurality of openingsinto which the current distribution layer extends, and the insulationlayer is formed as a filter layer that predominantly transmits anincident radiation within a first angular range and predominantlyreflects the incident radiation within a second angular range.
 17. Theradiation-emitting semiconductor chip according to claim 16, wherein atleast 60% of the incident radiation is transmitted.
 18. Aradiation-emitting semiconductor chip comprising: a semiconductor bodyhaving an active region that generates radiation; a first contact layerhaving a first contact surface for external electrical contacting of thesemiconductor chip and a first contact web structure connected to thefirst contact surface; a second contact layer having a second contactsurface for external electrical contacting of the semiconductor chip anda second contact web structure connected to the second contact surface,wherein 1) the first contact web structure and the second contact webstructure overlap in places in plan view of the semiconductor chip,wherein 2) the first contact layer, the second contact layer and aradiation exit surface are arranged at a same side on the semiconductorbody, 3) the first contact layer, the second contact layer, theradiation exit surface and a radiation exit side of the semiconductorchip are arranged at the same side of the semiconductor chip, and 4) theradiation is visible light, is produced in the active region and exitsthe semiconductor chip through the radiation exit surface and theradiation exit side; a current distribution layer through which a firstsemiconductor layer electrically conductively connects to the firstcontact layer; and an insulation layer containing a dielectric materialand arranged between the first semiconductor layer and the currentdistribution layer and has a plurality of openings into which thecurrent distribution layer extends, and the openings differ in shapeand/or size from one another.
 19. The radiation-emitting semiconductorchip according to claim 18, wherein a distribution density of theopenings is 200000 openings per mm² to 10 openings per mm².
 20. Theradiation-emitting semiconductor chip according to claim 18, wherein oneor more of the openings provided at an edge of the semiconductor chipare larger than openings in a middle portion of the semiconductor chip.